/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.mycat.calcite;

import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.sql.*;
import org.apache.calcite.sql.type.InferTypes;
import org.apache.calcite.sql.type.OperandTypes;
import org.apache.calcite.util.Pair;

import java.util.AbstractList;
import java.util.Map;

/**
 * SqlRowOperator represents the special ROW constructor.
 *
 * <p>TODO: describe usage for row-value construction and row-type construction
 * (SQL supports both).
 */
public class MycatSqlRowOperator extends SqlSpecialOperator {
    //~ Constructors -----------------------------------------------------------

    public MycatSqlRowOperator(String name) {
        super(name,
                SqlKind.OTHER, MDX_PRECEDENCE,
                false,
                null,
                InferTypes.RETURN_TYPE,
                OperandTypes.VARIADIC);
    }

    //~ Methods ----------------------------------------------------------------

    public RelDataType inferReturnType(
            final SqlOperatorBinding opBinding) {
        // The type of a ROW(e1,e2) expression is a record with the types
        // {e1type,e2type}.  According to the standard, field names are
        // implementation-defined.
        return opBinding.getTypeFactory().createStructType(
                new AbstractList<Map.Entry<String, RelDataType>>() {
                    public Map.Entry<String, RelDataType> get(int index) {
                        return Pair.of(
                                SqlUtil.deriveAliasFromOrdinal(index),
                                opBinding.getOperandType(index));
                    }

                    public int size() {
                        return opBinding.getOperandCount();
                    }
                });
    }

    public void unparse(
            SqlWriter writer,
            SqlCall call,
            int leftPrec,
            int rightPrec) {
        writer.print("ROW");
        final SqlWriter.Frame frame =
                writer.startList(SqlWriter.FrameTypeEnum.FUN_CALL, "(", ")");
        for (SqlNode operand : call.getOperandList()) {
            writer.sep(",");
            operand.unparse(writer, 0, 0);
        }
        writer.endList(frame);
    }

    // override SqlOperator
    public boolean requiresDecimalExpansion() {
        return false;
    }
}
